Effect of recycled polyethylene terephthalate (PET) fiber on the fracture resistance of asphalt mixtures

The incorporation of polyethylene terephthalate (PET) waste in the form of fiber is expected to provide asphalt mixtures with improved resistance to cracking. It has yet to be fully understood what relationship there is be-tween the fundamental properties of the PET fiber and cracking resistance of the asphalt mixture in service. Moreover, the usefulness of the current specification protocol based on the semi-circular bending (SCB) fracture test has not been well addressed. In order to shed light on these issues, the effects of PET properties (morphology, size and length), mixture properties (gradation and air void content), and testing conditions (temperature, loading rate) on the cracking resistance of asphalt mixture were systematically analyzed. It was found that the toughness of asphalt mixtures at different temperatures can be significantly improved if longer and thicker PET fibers with a rough surface are employed. In the case of high rates of loading, brittle fracture occurs in which cracks can develop through the coarse aggregate. Therefore, the contribution of PET fiber to cracking resistance of asphalt mixtures can not be observed. Hence, the loading rate in the current SCB standard test method should be reduced.

Automated summary

This study systematically analyzed the effects of PET fiber and asphalt mixture properties, as well as testing conditions, on the cracking resistance of asphalt mixtures. It was found that longer and thicker PET fibers with a rough surface can significantly improve the toughness of the asphalt mixtures. The loading rate in the current test method should be reduced.